
//for,Çó1µ½¸ø¶¨ÊýµÄºÍ,ÎÒÃ»ÓÐ¶¨ÒåÔËËã·û++£¬±ØÐëÐ´³öi=i+1
int main()

{
  int i,N,sum = 0;
  scanf(N);
  for(i=1;i<=N;i=i+1)
{

     sum = sum+i;
    }

  printf(sum);

}